[BUG] Correct "NEWLINE" Sequence on Windows is Shift+Enter

Environment

• Platform (select one):
• [ ] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [ x] Other: Windows
• Claude CLI version: 1.0.56
• Operating System: Windows 10+

Bug Description

In Claude Code, CTRL+ENTER produces a new line in the editor. However, on Windows, the standard for this is SHIFT+ENTER. This causes usability issues and often makes the user accidentally submit data before they are ready.

In fact, it's confusing my brain personally when entrering text now, and I just hit CTRL+ENTER in this window, which submitted the bug before I was ready.

Steps to Reproduce

1. Open Claude Code
2. Type something
3. Hit the Windows combination for a new line without submitting (SHIFT+ENTER)
4. Watch Claude submit the text for you before you were ready.

Expected Behavior

I expect SHIFT+ENTER to add a new line in the Windows editor

Actual Behavior

It submits the text instead.

Additional Context

Rollup of bugs #1262, #2754, #729, #3845, #2335 and many more.